Deposited thin films have major, diverse technological functions and enormous commercial value. There now exist diverse methods for vapor deposition of metals, semiconductors, insulators and organics, as well as complex multicomponents such as oxides and nitrides. In general, deposition methods fall into two classes. In Chemical Vapor Deposition (hereinafter, `CVD`), precursor molecules react at a heated substrate, usually at relatively high pressures, to generate species that comprise the deposited film. In Physical Vapor Deposition (hereinafter, `PVD`), the film species are generated some distance from the substrate, usually in a high vacuum; the gas phase mean free path is large, and film species travel by "line of sight" to deposit on the substrate.
Deposition techniques do not always fit this traditional description. The assignee of the present invention has developed a family of vapor deposition methods referred to as Jet Vapor Deposition (JVD), in which film species are made remotely, as in PVD, but the vacuum is "low", and the mean free path small, such as can be seen in issued U.S. Pat. No. 5,356,672 incorporated herein by reference in its entirety. Film components travel "line of sight" because they are convected in a sonic, collimated, "jet in low vacuum". Exemplary processes, based on patented JVD sonic nozzle sources such as the hot filament wirefeed, and the "electron jet" or "e-jet", include deposition of metals such as Cu, Au, Ag, Sn, Pb, Ni, Ti, Ta, and many others, singly or as alloys, in simple or multilayer form. Thus JVD can deposit many materials over large areas, by convecting film forming species from a nozzle to a substrate, by using multiple jets to make complex materials and structures, and by imposing relative jet-substrate motion to coat large areas with excellent uniformity.
It is also possible in JVD to convect species to a substrate or growing film that, just as in CVD, undergo film forming or film modifying reactions at the surface. The outstanding example in the JVD process is the deposition of extremely high quality silicon nitride, Si.sub.3 N.sub.4, at room temperature, using JPC's patented JVD microwave discharge source. Silicon nitride is an essential dielectric layer in integrated circuit fabrication, with the potential for greater future importance. In recent years, as device dimensions continue to shrink in successive generations of microelectronic devices, silicon nitride has been considered, because of its higher dielectric constant, as a possible replacement for silicon dioxide gate dielectric layers. Extensive efforts over many years have been aimed at exploiting silicon nitride's key properties, and most importantly, at devising a reliable deposition process suitable for semiconductor manufacturing. JVD, therefore, has enormous promise in the manufacturing of silicon nitride.
However, as explained later, JVD nitride deposition, in common with other plasma assisted nitride deposition processes, must be limited to low deposition rates if the film's requisite high quality is to be maintained. Deposition rate therefore becomes an economic issue; costly silicon wafers must be processed in multiple steps at economic throughputs. The present invention augments the deposition rate in the JVD nitride process without compromising JVD nitride quality.